Apoptosis, or programmed cell death, is an essential mechanism used throughout life to selectively eliminate cells, and deficient apoptotic cell death is associated with a wide variety of disorders encompassing most cell systems. Jacobson et al., Cell 88, 347-354 (1997). Fas (Apo-1/CD95) is a member of the tumor necrosis factor (TNF) receptor family, one of the main signaling systems with the specialized function of inducing apoptosis. Itoh et al., Cell 66, 233-243 (1991). Fas is a cell surface receptor that on activation (cross-linkage) by its natural ligand or by an agonistic antibody initiates a signaling cascade that leads to apoptosis. Yonehara et al., J. Exp. Med. 169, 1747-1756 (1989); Suda et al., Cell 75, 1169-1178 (1993). Impairment of Fas-linked signaling, and thus of apoptosis, appears to contribute to a variety of severe disorders associated, for example, with cell proliferation, inflammation and autoimmunity. Nagata, Cell 88, 355-365 (1997). Cancers, such as astrocytomas, which are among the most common lethal brain tumors, can express high levels of Fas and Fas ligand, but although often infiltrated by T cells, such infiltration does not improve patient prognosis, indicating that Fas apoptosis signaling may be dysfunctional. Saas et al., J. Clin. Invest. 99, 1173-1178 (1997); Weller et al., J. Clin. Invest. 94, 954-964 (1994). Impaired Fas-mediated apoptosis in lpr/lpr mice and gld/gld mice caused by mutations of the Fas or Fas ligand genes, respectively, results in lymphoproliferation and autoimmune disease, indicating that Fas-mediated signaling plays important parts in the induction of lymphocyte apoptosis and in the prevention of autoimmune disease. Watanabe-Fukunaga et al., Nature 356, 314-317 (1992); Takahashi et al., Cell 76, 969-976 (1994). Activation-induced cell death of T cells mediated by Fas-linked signaling is essential for down-modulating the T-cell response and the elimination of self-reactive T cells. Ju et al., Nature 373, 444-448 (1995); Brunner et al., Nature 373, 441-444 (1995); Dhein et al., Nature 373, 438-441 (1995). Thus, inadequate Fas-mediated apoptosis may contribute to proliferative disorders, and in T cells, could produce loss of T-cell tolerance resulting in the development of autoimmune disease.
The expression of Fas or of Fas ligand can regulate Fas-mediated apoptosis, but it is evident that differences in cell susceptibilities to Fas-mediated apoptosis also can be controlled by the regulation of signaling cascades, because not all Fas-positive cell types undergo apoptosis similarly after stimulation of Fas. Su et al., Immunity 2, 353-362 (1995); Miyawaki et al., J. Immunol. 149, 3753-3758 (1992). For example, activated T cells are more susceptible to Fas-mediated apoptosis than are naive T cells. Ehl et al., J. Immunol. 156, 2357-2360 (1996). Thus, interventions that facilitate Fas-induced apoptosis signaling processes may provide an ideal strategy for enhancing apoptosis for a variety of purposes, such as the elimination of self-reactive T cells in the treatment of autoimmune diseases. One advantage of this approach is that the intervention provides specificity for autoantigen-activated T cells that have failed to undergo activation-induced cell death, whereas the normal immune response to foreign antigens should remain less affected.
Prior art attempts to treat autoimmune diseases have primarily focused on down-regulating deleterious autoimmune reactions without affecting normal immune surveillance. These treatment modalities have focused on either the reestablishment of immune tolerance to autoantigens or to the suppression of T lymphocyte activity using immunosuppressive drugs including cyclosporin A, FK506 or rapamycin. Chatenoud, Mol. Med. Today 4, 25-30 (1998). However, these treatment modalities have critical disadvantages including the lack of antigen specificity and the adverse side effects of immunosuppressive therapy including susceptibility to infection and/or disease.
Accordingly, it would be advantageous and desirable to have a method of treatment of autoimmune disorders/diseases which is based on the observation that the total number of autoreactive T lymphocytes depends on a balance between the induction and proliferation of autoimmune T cells and their elimination by activation of an internal suicide program. This suicide program has been termed activation induced cell death (AICD). AICD is initiated in activated lymphocytes following re-stimulation by antigen and involves expression of death inducing ligands and receptors. Accordingly, Applicants have discovered that bisindolylmaleimide compounds can greatly increase the sensitivity of T cells to AICD.
Several bisindolylmaleimide derivatives, which were originally described as inhibitors of protein kinase C (PKC) (Toullec et al., J. Biol. Chem., 266, 1571-1581 (1991); Bit et al., J. Med. Chem. 36, 21-29 (1993); Jacobson et al., J. Pharmacol. Exp. Therap. 275, 995-1002 (1995); U.S. Pat. No. 5,821,072 to Schwartz et al. (also describes use of bisindolylmaleimides as potentiators of apoptosis in anti-tumor therapy); U.S. Pat. Nos. 5,292,747; 5,481,003; 5,491,242; 5,545,636; 5,552,396; 5,661,173; and 5,672,618), bisindolylmaleimide compounds were found to substantially facilitate Fas-mediated apoptosis in a human astrocytoma cell line and in several human T-cell lines. This facilitation of Fas-mediated apoptosis appears to be independent of PKC inhibition. Facilitation of Fas-mediated apoptosis resulted in increased activation-induced cell death of activated T cells and this effect was specific for Fas- and tumor necrosis factor (TNF)-mediated apoptosis.
The use of some bisindolylmaleimides has been disclosed in the treatment of inflammatory, immunological, bronchopulmonary or cardiovascular disorders (see U.S. Pat. No. 5,057,614 to Davis et al.). In vivo administration of bisindolylmaleimide VIII to rats during autoantigen stimulation was found to almost completely block the development of autoimmune diseases in two models: the Lewis rat model of experimental allergic encephalitis (EAE), and the Lewis adjuvant arthritis model.